The present disclosure is related to prosthetic heart valve replacement, and more particularly to devices, systems, and methods for delivery of collapsible prosthetic heart valves.
Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery.
Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valve structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, generally the valve is first collapsed or crimped to reduce its circumferential size.
When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient's heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the outer sheath covering the valve is withdrawn.
In conventional delivery systems for self-expanding aortic valves, for example, after the delivery system has been positioned for deployment, the annulus end of the valve is typically unsheathed and expanded first, while the aortic end of the valve remains sheathed. Once the annulus end of the valve has expanded, it may be determined that the valve needs to be repositioned in the patient's aortic annulus. To accomplish this, a user (such as a surgeon or an interventional cardiologist) typically resheathes the annulus end of the valve, so that the valve can be repositioned while in a collapsed state. After the valve has been repositioned, the user can again release the valve.
In traditional deployment methods, the user operates a handle to cause distal or proximal movement of a catheter or other member within the handle, resulting in relative movement between the prosthetic valve and an outer sheath covering the prosthetic valve so as to cause deployment of the valve. For example, in a typical transfemoral delivery device, a distal end of an outer sheath surrounds the prosthetic valve, and a proximal end of the outer sheath may be fixed to a carriage within the handle. Manipulation of the handle causes the carriage to move proximally or distally, which in turn causes proximal or distal movement of the outer sheath. In a typical transapical delivery device, a distal end of an inner shaft may support the prosthetic valve, and a proximal end of the inner shaft may be attached to a carriage within the handle, while the outer sheath may be fixedly connected at its proximal end to the handle. Manipulation of the handle causes the carriage to move proximally or distally, which in turn causes proximal or distal movement of the inner shaft relative to the outer sheath. In both examples above, manipulation of the delivery device handle causes proximal or distal movement of a carriage, which movement is translated along most or all of the length of the device, through either the outer sheath or inner shaft.